JP2006046434A - Wheel bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wheel bearing device with an inner ring having improved durability and reliability by restricting hooping stress on the inner ring in a caulking process to a fixed value or smaller. <P>SOLUTION: In the wheel bearing device in a self-retaining structure, the inner ring 3 is pressed into a small diameter step 2b of a hub ring 2 and the inner ring 3 is fixed to the hub ring 2 in the axial direction with a caulked portion 2c formed by plastically deforming the end of the small diameter step 2b outward to the radial direction. The outer diameter 11b of the inner ring 3 is measured before and after plastically being deformed, and the amount of its expansion is used for managing the hooping stress on the inner ring 3 in accordance with a proportional relationship composed of a preset primary function and restricting the hooping stress to be a preset value or smaller. Thus, the hooping stress on the inner ring 3 caulked and fixed to the hub ring 2 is easily and accurately managed and the crack or delayed destruction of the inner ring 3 is prevented. As a result, the inner ring 3 has improved durability and reliability. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wheel bearing device that rotatably supports a wheel of an automobile or the like with respect to a suspension device, and more particularly to a wheel bearing device that improves durability of an inner ring that is crimped and fixed to a hub wheel. .

  2. Description of the Related Art Wheel bearing devices for vehicles such as automobiles include those for driving wheels and those for driven wheels. In particular, a wheel bearing device that rotatably supports a wheel with respect to a suspension device of an automobile has been made lighter and more compact for improving fuel efficiency, not to mention cost reduction. As a typical example of the conventional structure, a wheel bearing device for a driven wheel as shown in FIG. 6 is known.

  This wheel bearing device is referred to as a third generation, and includes a hub wheel 51, an inner ring 52, an outer ring 53, and double row rolling elements 54, 54. The hub wheel 51 integrally has a wheel mounting flange 55 for mounting a wheel (not shown) at one end thereof, an inner rolling surface 51a on the outer periphery, and a small diameter extending in the axial direction from the inner rolling surface 51a. A step portion 51b is formed. Further, hub bolts 56 for fixing the wheels are planted at the circumferentially equidistant positions of the wheel mounting flanges 55.

  An inner ring 52 having an inner rolling surface 52a formed on the outer periphery is press-fitted into the small diameter step portion 51b of the hub wheel 51. The inner ring 52 is prevented from coming off from the hub wheel 51 in the axial direction by a caulking portion 51c formed by plastically deforming the end portion of the small diameter step portion 51b of the hub wheel 51 radially outward. .

  The outer ring 53 integrally has a vehicle body mounting flange 53b on the outer periphery, and double row outer rolling surfaces 53a and 53a are formed on the inner periphery. Between the inner rolling surfaces 51a and 52a facing the double-row outer rolling surfaces 53a and 53a, double-row rolling elements 54 and 54 are accommodated so as to roll freely.

  The hub wheel 51 is integrally formed by forging a carbon steel material having a carbon content of 0.40 to 0.80% by weight, and a portion indicated by an oblique lattice, that is, a wheel mounting flange 55. The surface is hardened by induction hardening or the like from the base portion to the inner rolling surface 51a and the small diameter step portion 51b. In addition, the caulking part 51c is left with the raw material surface hardness after forging. On the other hand, the inner ring 52 is made of high carbon steel such as high carbon chromium bearing steel such as SUJ2, and is hardened and hardened to the core.

As a result, a wheel bearing device having sufficient durability can be realized at low cost, and the caulking portion 51c is prevented from being damaged such as a crack, and is fixed to the hub wheel 51 by the caulking portion 51c. It is possible to prevent the diameter of the inner ring 52 from changing to an extent that causes a practical problem. And while reducing possibility that this inner ring | wheel 52 will be damaged with the fixing operation | work, a preload can be maintained to an appropriate value, and also cost reduction can be aimed at by reduction of a number of parts, parts processing, and an assembly man-hour.
JP-A-11-129703

  In such a conventional wheel bearing device, the force that greatly deforms the inner diameter of the inner ring 52 is prevented so as to affect the durability such as the preload and the rolling fatigue life accompanying the caulking work. be able to. However, when the end portion of the small diameter step portion 51b is plastically deformed radially outward to form the crimping portion 51c, the vicinity of the crimping portion 51c of the small diameter step portion 51c is also plastically deformed in the radial direction. With the plastic deformation, the inner diameter of the inner ring 52 is expanded, and it cannot be denied that a hoop stress is generated in the outer diameter 57 of the inner ring 52.

  As means for lowering the hoop stress, it has also been proposed to variously change the end shape of the small-diameter stepped portion 51b of the hub wheel 51 to suppress the amount of plastic deformation at the time of swing caulking. Even when a large moment load or the like is applied, the crimped portion 51c is required to have a strength sufficient to firmly fix the inner ring 52. Therefore, it is said that the amount of plastic deformation is suppressed and the strength of the crimped portion is secured. There are conflicting issues.

  When a hoop stress is generated in the outer diameter 57 of the inner ring 52, when corrosion occurs in this portion, diffusible hydrogen existing in the environment enters the structure of the inner ring 52 and the metal grain boundary is destroyed, so-called “delay”. “Destruction” tends to occur, which is not preferable.

  Conventionally, as a method for measuring the hoop stress itself, for example, the outer diameter 57 of the inner ring 52 that maximizes the hoop stress can be irradiated with X-rays or a strain gauge can be attached. In view of this, the work is complicated and inefficient.

  The present invention has been made in view of such conventional problems, and a wheel bearing in which the hoop stress generated in the inner ring in the caulking process is regulated to a certain value or less and the durability and reliability of the inner ring are improved. An object is to provide an apparatus.

  In order to achieve such an object, the invention according to claim 1 of the present invention integrally has an outer member having a double row outer rolling surface formed on the inner periphery and a wheel mounting flange at one end. A hub wheel formed with a small-diameter step portion extending in the axial direction from the wheel mounting flange, and an inner ring press-fitted into the small-diameter step portion of the hub wheel, and opposed to the outer surface of the double row on the outer periphery. An inner member in which a double row inner rolling surface is formed, and a double row rolling element accommodated between the inner member and the outer member via a cage between the rolling surfaces of the inner member and the outer member. A wheel bearing device in which the inner ring is axially fixed by a caulking portion formed by plastically deforming an end portion of the small-diameter stepped portion radially outward. The diameter is measured, and the amount of expansion of the outer diameter of the inner ring is generated in the inner ring based on the relationship obtained in advance. Hoop stress is managed, the hoop stress is adopted a structure that is regulated to a predetermined value or less.

  In this way, the inner ring is fixed to the hub ring in the axial direction by the caulking portion formed by press-fitting the inner ring into the small-diameter step portion of the hub wheel and plastically deforming the end of the small-diameter step portion radially outward. In the so-called self-retained wheel bearing device, the outer diameter of the inner ring before and after plastic deformation is measured, and a hoop generated in the inner ring based on a predetermined relationship with the amount of expansion of the outer diameter of the inner ring. Since the stress is controlled and the hoop stress is regulated to a predetermined value or less, the hoop stress of the inner ring crimped and fixed to the hub ring can be managed very easily and accurately, and the inner ring is cracked or The occurrence of delayed fracture can be prevented, and a wheel bearing device with improved durability and reliability of the inner ring can be provided.

  Preferably, as in the invention described in claim 2, the relationship between the amount of expansion of the outer diameter of the inner ring due to the plastic deformation and the hoop stress generated in the inner ring is set to a proportional relationship consisting of a predetermined linear function. For example, the hoop stress itself generated in the inner ring can be easily and accurately measured.

  According to a third aspect of the present invention, the hub wheel is made of medium carbon steel containing 0.40 to 0.80% by weight of carbon, and is surfaced by induction hardening from the inner rolling surface to the small diameter step portion. The hardened portion is hardened in the range of 58 to 64 HRC, the caulking portion is an unquenched portion having a material surface hardness of 25 HRC or less after forging, and the inner ring is made of a high carbon chrome bearing steel. Since the core is hardened in the range of 58 to 64 HRC, the hoop stress of the inner ring generated by caulking can be easily and accurately suppressed to a predetermined value, for example, 250 MPa or less.

  According to a fourth aspect of the present invention, since a small-diameter stepped portion is formed on the inboard side of the inner ring outer diameter, the stepped portion is exposed to a corrosive environment without being attached with a seal. The amount can be controlled and the hoop stress can be regulated below a predetermined value.

  Further, in the invention according to claim 5, since an annular recess is formed in a portion corresponding to the inboard side of the inner ring on the outer periphery of the end portion of the small diameter step portion before the caulking, The caulking process can suppress deformation of the outer diameter portion of the inner ring, in particular, the stepped portion on the inboard side, increase the strength of the caulking portion, and reduce hoop stress generated in the inner ring.

  The wheel bearing device according to the present invention integrally has an outer member having a double row outer raceway formed on the inner periphery and a wheel mounting flange at one end, and extends in an axial direction from the wheel mounting flange. A hub ring formed with a small-diameter step portion and an inner ring press-fitted into the small-diameter step portion of the hub ring, and a double-row inner rolling surface facing the double-row outer rolling surface is formed on the outer periphery. An inner member, and a double-row rolling element that is rotatably accommodated between the rolling surfaces of the inner member and the outer member via a cage, and an end portion of the small-diameter step portion. In a wheel bearing device in which the inner ring is fixed in the axial direction by a caulking portion formed by plastic deformation of the outer ring in the radial direction, the outer diameter of the inner ring before and after the plastic deformation is measured, and the amount of expansion is expressed as follows. Therefore, the hoop stress generated in the inner ring is managed based on the relationship obtained in advance. Since it is regulated below a predetermined value, the hoop stress of the inner ring that is crimped and fixed to the hub ring can be managed very easily and accurately, and the occurrence of cracking or delayed fracture of the inner ring can be prevented. It is possible to provide a wheel bearing device with improved durability and reliability of the inner ring.

  A vehicle body mounting flange is integrally formed on the outer periphery, an outer member having a double row outer rolling surface formed on the inner periphery, a wheel mounting flange is integrally formed on one end, and the double row outer rolling is formed on the outer periphery. One inner rolling surface facing the running surface, a hub wheel formed with a small-diameter step portion extending in the axial direction from the inner rolling surface, and press-fitted into the small-diameter step portion of the hub wheel, and the double row on the outer periphery An inner member comprising an inner ring formed with the other inner rolling surface opposite to the outer rolling surface of the inner rolling surface, and rolling between the both rolling surfaces of the inner member and the outer member via a cage. A wheel bearing device including a double row rolling element accommodated freely, wherein the inner ring is fixed in an axial direction by a caulking portion formed by plastically deforming an end portion of the small diameter step portion radially outward. The outer diameter of the inner ring before and after the plastic deformation is measured, and is set in advance by the amount of expansion of the outer diameter of the inner ring. Hoop stress is managed exhibited by the inner ring based on a proportional relation of the constant of the linear function, the hoop stress is regulated to a predetermined value or less.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an embodiment of a wheel bearing device according to the present invention. In the following description, the side closer to the outer side of the vehicle when assembled to the vehicle is referred to as the outboard side (left side in the drawing), and the side closer to the center is referred to as the inboard side (right side in the drawing).

  This wheel bearing device is referred to as the third generation on the drive wheel side, and is a double row rolling element (ball) accommodated in a freely rollable manner between the inner member 1, the outer member 10, and both members 1, 10. 6 and 6. The inner member 1 includes a hub ring 2 and an inner ring 3 that is press-fitted into the hub ring 2 through a predetermined scissors.

  The hub wheel 2 integrally has a wheel mounting flange 4 for mounting a wheel (not shown) at an end portion on the outboard side, and is used for fixing the wheel at a circumferentially equidistant position of the wheel mounting flange 4. Hub bolts 5 are planted. Further, on the outer periphery of the hub wheel 2, an inner rolling surface 2a and a cylindrical small-diameter step portion 2b extending in the axial direction from the inner rolling surface 2a are formed. The inner ring 3 having the inner raceway surface 3a formed on the outer periphery is press-fitted into the small-diameter step portion 2b, and the end portion of the small-diameter step portion 2b is plastically deformed outward in the radial direction. Thus, the inner ring 3 is prevented from coming off in the axial direction with respect to the hub ring 2.

  The outer member 10 integrally has a vehicle body mounting flange 10b for mounting to a vehicle body (not shown) on the outer periphery, and double row outer rolling surfaces 10a, 10a are formed on the inner periphery. And the double row rolling elements 6 and 6 are accommodated between each rolling surface 10a, 2a and 10a, 3a, and these double row rolling elements 6 and 6 are rollably hold | maintained by the holder | retainers 7 and 7. ing. Further, seals 8 and 9 are attached to the end portion of the outer member 10 to prevent leakage of the lubricating grease sealed inside the bearing and intrusion of rainwater, dust and the like from the outside into the bearing.

  Here, the wheel bearing device referred to as the third generation in which the inner raceway surface 2a is directly formed on the outer periphery of the hub wheel 2 is illustrated, but the wheel bearing device according to the present invention is not limited to such a structure. For example, it may be a first generation or second generation structure in which a pair of inner rings are press-fitted into a small diameter step portion of a hub ring. In addition, although the double row angular contact ball bearing which used the rolling elements 6 and 6 as the ball | bowl was illustrated, it is not restricted to this, The double row tapered roller bearing which uses a tapered roller for a rolling element may be sufficient.

  The hub wheel 2 is made of medium carbon steel containing carbon of 0.40 to 0.80% by weight, such as S53C, and includes an inner rolling surface 2a on the outboard side, a seal land portion with which the seal 8 is in sliding contact, and a small diameter. The surface hardness is set to a range of 58 to 64 HRC by induction hardening over the step 2b. The caulking portion 2c is an unquenched portion having a material surface hardness of 25 HRC or less after forging. On the other hand, the inner ring 3 is made of high carbon chrome bearing steel such as SUJ2, and is hardened in the range of 58 to 64 HRC up to the core part by quenching.

  The outer member 10 is formed of medium carbon steel containing 0.40 to 0.80% by weight of carbon, such as S53C, like the hub wheel 2, and the double row outer raceway surfaces 10a and 10a are formed by induction hardening. The surface hardness is set in the range of 58 to 64 HRC.

  The applicant analyzes the cause of the occurrence of the hoop stress σ in the outer diameter portion 11 of the inner ring 3 and the relationship between the hoop stress σ generated by the crimping process and the radial expansion amount δ of the outer diameter portion 11 in the inner ring 3. As a result of the investigation focusing on the above, it has been found that the expansion amount δ of the outer diameter portion 11 increases as the hoop stress σ increases by caulking. Then, it was found that the relationship between the two is a substantially linear proportional relationship as shown in FIG. Therefore, it was verified that the hoop stress σ generated in the inner ring 3 can be regulated to a predetermined value or less by managing the radial expansion amount δ of the outer diameter portion 11 in the inner ring 3. On the other hand, the hoop stress needs to be controlled to 250 MPa or less when the inner ring 3 is used in an exposed state to the external environment.

  As can be seen from this figure, in order to restrict the hoop stress σ in the outer diameter portion 11 of the inner ring 3 generated by the caulking process to, for example, 250 MPa or less, the radial expansion amount of the outer diameter portion 11 of the inner ring 3 is reduced. It can be seen that δ should be managed to be 75 μm or less. In other words, 75 μm or less is OK, and products exceeding 75 μm are NG. By adopting such a method, the hoop stress σ of the inner ring 3 crimped and fixed to the hub ring 2 can be managed very easily and accurately, and the hoop stress σ of the inner ring 3 is regulated to a predetermined value or less. be able to. Therefore, it is possible to provide a wheel bearing device that can prevent the inner ring 3 from being cracked or delayed and can improve the durability and reliability of the inner ring 3 that is crimped and fixed to the hub ring 2.

  Here, the regulation value of the hoop stress σ is 250 MPa, but this is a case where the inner ring 3 is exposed to the external environment. For example, although not shown, like the wheel bearing device on the driven wheel side, When the inner ring is sealed with an end cap or the like, the regulation value may be 300 MPa.

  Since the outer diameter portion 11 has the largest hoop stress σ of the inner ring 3, in this embodiment, as shown in FIG. 3B, the fitting in which the seal 9 is fitted in the outer diameter portion 11 of the inner ring 3. A small-diameter stepped portion 11b is formed on the inboard side from the portion 11a. Thereby, the hoop stress σ of the inner ring 3 can be regulated to a predetermined value or less by managing the expansion amount δ of the stepped portion 11b exposed to at least a corrosive environment. In addition, although the inner ring | wheel 3 in which the stepped part 11b was formed in the outer diameter part 11 was illustrated here, not only this but the structure which does not form the stepped part 11b may be sufficient.

  In FIG. 2, the amount of expansion δ of the stepped portion 11b of the inner ring 3 is measured after the stepped portion 11b of the inner ring 3 alone, as shown in FIG. 3 (a), and after caulking, as shown in (b). The stepped portion 11b of the inner ring 3 is measured, and the difference in outer diameter is used as the expansion amount δ. In addition, as shown in FIG. 4, it is good also considering the variation | change_quantity of the step part 11b before and behind crimping as an expansion amount (delta). Here, the measurement position of the expansion amount δ in the stepped portion 11b is set by measuring a measurement point P having a predetermined distance e from the large end surface 3b in advance as shown in FIG. 5 in order to increase the reliability of the measurement data. It is desirable to keep it.

  Further, since it has been found that the expansion amount δ of the outer diameter portion 11 in the inner ring 3 increases toward the inboard side, in this embodiment, as shown in FIG. An annular recess 13 is formed in the end 12 of the 2b at a portion corresponding to the inboard side of the inner ring 3 on the outer periphery. As a result, the deformation of the outer diameter portion 11 of the inner ring 3, in particular, the stepped portion 11 b on the inboard side, can be suppressed by the caulking process, the strength of the caulking portion 2 c is increased, and the hoop generated in the inner ring 3 The stress σ can be reduced. Here, the strength of the caulking portion 2c is defined by, for example, the pushing amount of the inner ring 3 that generates an axial force of 20 kN or more.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  In the wheel bearing device according to the present invention, the inner ring is fixed by a caulking portion formed by press-fitting an inner ring into a small-diameter step portion of a hub wheel and plastically deforming an end portion of the small-diameter step portion. It can be applied to a self-retained wheel bearing device.

It is a longitudinal section showing one embodiment of a wheel bearing device concerning the present invention. It is a graph which shows the relationship between the hoop stress of the inner ring | wheel produced | generated by a crimping process, and the radial direction expansion amount of the outer diameter part in an inner ring | wheel. It is explanatory drawing which shows the measurement point of the expansion amount of an inner ring | wheel outer diameter, (a) shows the measurement of the outer diameter in an inner ring single-piece | unit, (b) has shown the measurement of the inner ring outer diameter after crimping. It is explanatory drawing which shows the other measuring point of the expansion amount of an inner ring outer diameter, (a) shows the measurement of the inner ring outer diameter before crimping, (b) shows the measurement of the inner ring outer diameter after crimping. . It is explanatory drawing which shows the measurement position for measuring the expansion amount of an inner ring outer diameter. It is a longitudinal cross-sectional view which shows the conventional wheel bearing apparatus.

Explanation of symbols

1 ... inner member 2 ... hub wheels 2a, 3a ... inner rolling surface 2b ... small diameter step 2c ·································································… ································································································································· -Outer member 10a ... Outer rolling surface 10b ... Car body mounting flange 11 ... Outer diameter part 11a ... Fitting part 11b .... Stepped part 12 ... End 13 ... Recess 51 ... Hub wheels 51a, 52a ... Inner rolling surface 51b... Small diameter step 51c. .... Stepped part 52 ... Inner ring 53 ... Outer ring 53a ... Outer rolling surface 53b ... Car body Mounting flange 54 ... Rolling element 55 ... Wheel mounting flange 56 ... Hub bolt 57 ... Outer diameter e ...・ ・ ・ ・ ・ ・ Distance P from inner ring large end surface ・ ・ ・ ・ ・ ・ ・ ・ ・ Measurement point δ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Expansion amount σ ・ ・ ・ ・ ・ ・ ・ ・ ・ Hoop stress

Claims (5)

An outer member having a double row outer raceway formed on the inner periphery;
A hub wheel integrally having a wheel mounting flange at one end, and having a small-diameter step portion extending in the axial direction from the wheel mounting flange,
And an inner member press-fitted into the small-diameter step portion of the hub wheel, and an inner member in which a double-row inner rolling surface facing the double-row outer rolling surface is formed on the outer periphery,
A double-row rolling element accommodated between the rolling surfaces of the inner member and the outer member via a cage so as to freely roll,
In the wheel bearing device in which the inner ring is fixed in the axial direction by a caulking portion formed by plastically deforming an end portion of the small diameter step portion radially outward,
The outer diameter of the inner ring before and after the plastic deformation is measured, and the amount of expansion of the outer diameter of the inner ring is used to manage the hoop stress generated in the inner ring based on a predetermined relationship, and the hoop stress is a predetermined value. A bearing device for a wheel, which is regulated as follows.   2. The wheel bearing device according to claim 1, wherein a relationship between an amount of expansion of the outer diameter of the inner ring due to the plastic deformation and a hoop stress generated in the inner ring is set to a proportional relationship including a predetermined linear function.   The hub ring is made of medium carbon steel containing 0.40 to 0.80% by weight of carbon, and the surface hardness is set to a range of 58 to 64 HRC by induction hardening from the inner rolling surface to the small diameter step portion. The caulking portion is a non-hardened portion having a surface hardness of 25 HRC or less after forging, and the inner ring is made of high carbon chrome bearing steel, and is hardened in a range of 58 to 64 HRC to the core portion by quenching. The wheel bearing device according to claim 1, wherein the wheel bearing device is provided.   The wheel bearing device according to any one of claims 1 to 3, wherein a step portion having a small diameter is formed on an inboard side of the inner ring outer diameter.   The wheel bearing according to any one of claims 1 to 4, wherein an annular recess is formed at a portion of the outer periphery corresponding to the inboard side of the inner ring at an end of the small-diameter step portion before the caulking. apparatus.

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